The present invention relates to an intravascular medical catheter and a method of manufacturing an intravascular medical catheter. More specifically, the present invention relates to a medical catheter having relatively good flexibility, strength and durability, as well as, improved tracking and movement within a vessel.
A number of intravascular procedures are currently utilized to treat a stenosis within a body vessel of a human being. A common intravascular procedure is referred to a percutaneous transluminal coronary angioplasty (hereinafter xe2x80x9cangioplastyxe2x80x9d). During a typical angioplasty procedure, a guidewire is initially positioned within the body vessel and a guiding catheter is positioned over the guidewire. Next, a balloon catheter having an inflatable balloon is advanced through the guiding catheter and vessel until the balloon is adjacent to the stenosis. Subsequently, inflation of the balloon compresses the stenosis and dilates the body vessel.
Typically, the body vessel is curved and has a relatively small inner diameter. Therefore, a physician often needs to rotate a distal end of the catheter to navigate through the curved body vessel. As a result thereof, the medical catheter must have good torsional strength so that the distal end of the catheter rotates upon rotation of a proximal end of catheter. Presently, most guiding catheters include a catheter shaft having flexible inner liner, a braided wire mesh wrapped around the inner liner and a flexible outer shell. The braided wire mesh and the outer shell are relatively stiff and provide torsional strength to the catheter shaft. Unfortunately, the distal end of the catheter shaft is also relatively stiff and the catheter shaft is often difficult to move in the vessel.
One attempt to solve this problem involves adding one or more separate, tubular, soft tips onto the distal end of the catheter shaft. The soft tips are made of a polymer having a lower hardness than the catheter shaft. Unfortunately, the transition from the catheter shaft to the soft tip is relatively stiff and inflexible. Further, the transition between the relatively hard catheter shaft and the soft tip is subject to collapse and kinking during movement in the vessel. As a result thereof, this solution is not entirely satisfactory.
In light of the above, it is an object of the present invention to provide an improved medical catheter having relatively good movement and tracking in the body vessel. Another object of the present invention is to provide a medical catheter having a good transition between the relatively stiff catheter shaft and a flexible soft tip. Still another object of the present invention is to provide a medical catheter having good flexibility, durability, and torsional strength characteristics. Yet another object of the present invention is to provide a medical catheter which is relatively easy and inexpensive to manufacture.
The present invention is directed to a medical catheter useful for an intervascular procedure which satisfies these objectives. The medical catheter includes a catheter shaft having a tubular inner liner, a reinforcing section and an outer shell. As provided herein, the catheter shaft includes a circumferential groove in the outer shell near a distal end of the catheter shaft. The groove encircles a portion of the reinforcing section and provides flexibility to the catheter shaft without compromising the torsional strength of the catheter shaft. As a result thereof, the medical catheter is easier to move in the body vessel and resists kinking.
The reinforcing section contacts and encircles the inner liner. Further, the reinforcing section provides torsional strength to the catheter shaft. The outer shell is formed over the reinforcing section and encircles the reinforcing section. Because the groove is formed in the outer shell, the torsional strength of the reinforcing section is not effected. This allows for smoother transition at the distal end of the catheter shaft.
In one embodiment, the groove is annular shaped and has a groove depth which is equal to a thickness of the outer shell. In another embodiment, the groove is helical shaped. Preferably, the groove is cut out of the outer shell with a laser after the outer shell is extruded over the reinforcing section. The use of a laser allows the outer shell to be removed without damaging the reinforcing section.
The medical catheter can include a fill section which fills a portion of the groove. The fill section is preferably made of a material having a hardness which is less than a hardness of the outer shell. This allows the distal end of the catheter shaft to be more flexible than the rest of the catheter shaft. Further, because the reinforcing section is continuous under the fill section, the flexibility of the medical catheter is enhanced without compromising the torsional strength at the distal end of the catheter shaft.
The present invention is also a method for making a medical catheter. The method includes providing a catheter shaft, and forming a groove in the catheter shaft near the distal end with a laser. The groove encircles the reinforcing section and provides flexibility to the catheter shaft near the distal end. Further, as provided herein, the groove can be filled with a fill section to provide a transitional region of hardness near the distal end of the catheter shaft.
Importantly, the medical catheter provided herein has good movement and tracking in the vessel and good strength and durability characteristics. Further, the medical catheter resists kinking and has relatively good torsional strength.